# SM4 Block Cipher Algorithm
# See GM/T 0002-2012《SM4分组密码算法》

from .base import BlockCipher
from struct import pack, unpack
from array import array

# Expanded SM4 S-boxes	Sbox table: 8bits input convert to 8 bits output
Sbox = bytes((
	0xd6, 0x90, 0xe9, 0xfe, 0xcc, 0xe1, 0x3d, 0xb7, 0x16, 0xb6, 0x14, 0xc2, 0x28, 0xfb, 0x2c, 0x05,
	0x2b, 0x67, 0x9a, 0x76, 0x2a, 0xbe, 0x04, 0xc3, 0xaa, 0x44, 0x13, 0x26, 0x49, 0x86, 0x06, 0x99,
	0x9c, 0x42, 0x50, 0xf4, 0x91, 0xef, 0x98, 0x7a, 0x33, 0x54, 0x0b, 0x43, 0xed, 0xcf, 0xac, 0x62,
	0xe4, 0xb3, 0x1c, 0xa9, 0xc9, 0x08, 0xe8, 0x95, 0x80, 0xdf, 0x94, 0xfa, 0x75, 0x8f, 0x3f, 0xa6,
	0x47, 0x07, 0xa7, 0xfc, 0xf3, 0x73, 0x17, 0xba, 0x83, 0x59, 0x3c, 0x19, 0xe6, 0x85, 0x4f, 0xa8,
	0x68, 0x6b, 0x81, 0xb2, 0x71, 0x64, 0xda, 0x8b, 0xf8, 0xeb, 0x0f, 0x4b, 0x70, 0x56, 0x9d, 0x35,
	0x1e, 0x24, 0x0e, 0x5e, 0x63, 0x58, 0xd1, 0xa2, 0x25, 0x22, 0x7c, 0x3b, 0x01, 0x21, 0x78, 0x87,
	0xd4, 0x00, 0x46, 0x57, 0x9f, 0xd3, 0x27, 0x52, 0x4c, 0x36, 0x02, 0xe7, 0xa0, 0xc4, 0xc8, 0x9e,
	0xea, 0xbf, 0x8a, 0xd2, 0x40, 0xc7, 0x38, 0xb5, 0xa3, 0xf7, 0xf2, 0xce, 0xf9, 0x61, 0x15, 0xa1,
	0xe0, 0xae, 0x5d, 0xa4, 0x9b, 0x34, 0x1a, 0x55, 0xad, 0x93, 0x32, 0x30, 0xf5, 0x8c, 0xb1, 0xe3,
	0x1d, 0xf6, 0xe2, 0x2e, 0x82, 0x66, 0xca, 0x60, 0xc0, 0x29, 0x23, 0xab, 0x0d, 0x53, 0x4e, 0x6f,
	0xd5, 0xdb, 0x37, 0x45, 0xde, 0xfd, 0x8e, 0x2f, 0x03, 0xff, 0x6a, 0x72, 0x6d, 0x6c, 0x5b, 0x51,
	0x8d, 0x1b, 0xaf, 0x92, 0xbb, 0xdd, 0xbc, 0x7f, 0x11, 0xd9, 0x5c, 0x41, 0x1f, 0x10, 0x5a, 0xd8,
	0x0a, 0xc1, 0x31, 0x88, 0xa5, 0xcd, 0x7b, 0xbd, 0x2d, 0x74, 0xd0, 0x12, 0xb8, 0xe5, 0xb4, 0xb0,
	0x89, 0x69, 0x97, 0x4a, 0x0c, 0x96, 0x77, 0x7e, 0x65, 0xb9, 0xf1, 0x09, 0xc5, 0x6e, 0xc6, 0x84,
	0x18, 0xf0, 0x7d, 0xec, 0x3a, 0xdc, 0x4d, 0x20, 0x79, 0xee, 0x5f, 0x3e, 0xd7, 0xcb, 0x39, 0x48
))

# System parameter
FK = array('I', (0xa3b1bac6, 0x56aa3350, 0x677d9197, 0xb27022dc))

# fixed parameter
CK = array('I', (
	0x00070e15, 0x1c232a31, 0x383f464d, 0x545b6269,
	0x70777e85, 0x8c939aa1, 0xa8afb6bd, 0xc4cbd2d9,
	0xe0e7eef5, 0xfc030a11, 0x181f262d, 0x343b4249,
	0x50575e65, 0x6c737a81, 0x888f969d, 0xa4abb2b9,
	0xc0c7ced5, 0xdce3eaf1, 0xf8ff060d, 0x141b2229,
	0x30373e45, 0x4c535a61, 0x686f767d, 0x848b9299,
	0xa0a7aeb5, 0xbcc3cad1, 0xd8dfe6ed, 0xf4fb0209,
	0x10171e25, 0x2c333a41, 0x484f565d, 0x646b7279
))

def ROT32L(i32, n) :
	return i32 << n & 0xffffffff | i32 >> 32-n

def F(x1, x2, x3, x4, k, table=Sbox, L=lambda B: \
	ROT32L(B, 2) ^ ROT32L(B, 10) ^ ROT32L(B, 18) ^ ROT32L(B, 24)
) :
	i32 = x2 ^ x3 ^ x4 ^ k
	B = (
		table[i32>>24       ] << 24 |
		table[i32>>16 & 0xff] << 16 |
		table[i32>> 8 & 0xff] <<  8 |
		table[i32     & 0xff]
	)
	return x1 ^ B ^ L(B)
	

class SM4(BlockCipher) :
	__slots__ = ('K', 'iK') + BlockCipher.__slots__
	
	def __new__(cls, key, mode=BlockCipher.MODE_ECB, iv=bytes(16)) :
		self = super().__new__(cls, mode, iv)
		if len(key) != 16 :
			raise ValueError('key must be length 16 bytes')
		
		self.K = array('I') # = 32 bit = 4 bytes
		w1, w2, w3, w4 = unpack(b'>IIII', key)
		w1, w2, w3, w4 = w1^FK[0], w2^FK[1], w3^FK[2], w4^FK[3]
		for i in CK :
			w1, w2, w3, w4 = \
				w2, w3, w4, F(w1, w2, w3, w4, i, L=\
					lambda B: ROT32L(B, 13) ^ ROT32L(B, 23))
			self.K.append(w4)
		
		self.iK = self.K[::-1]
		
		return self
		
	def encrypt_block(self, block) :
		w1, w2, w3, w4 = unpack(b'>IIII', block)
		for k in self.K :
			w1, w2, w3, w4 = \
				w2, w3, w4, F(w1, w2, w3, w4, k)
		return pack(b'>IIII', w4, w3, w2, w1)
		
	def decrypt_block(self, block) :
		w1, w2, w3, w4 = unpack(b'>IIII', block)
		for k in self.iK :
			w1, w2, w3, w4 = \
				w2, w3, w4, F(w1, w2, w3, w4, k)
		return pack(b'>IIII', w4, w3, w2, w1)
	
	block_size = 16
